S3 and Nvidia are at each others' throats today, following the launch of legal action against its rival by Nvidia for alleged patent infringement. The suit was filed last week with the US District Court for Northern California in San Francisco and assigned to Judge Vaughn R Walker -- the judge who presided over Apple's 1988 GUI copyright infringement case against Hewlett-Packard and Microsoft, and ruled in the defendants' favour. This time, Nvidia is asking for a jury to adjudicate. Nvidia wouldn't say why it had launched the action -- "You'll have to call S3," said a company spokesman -- or reveal its grounds for claiming S3 has violated its intellectual property. We did, but no one from S3 was available for comment as we went to press, which isn't surprising since the company has still digesting details of its decision to buy 3D graphics specialist Number Nine. We suspect -- and given the silence from both parties it is just a suspicion -- that the case may centre on S3's transform and lighting engine, a key part of its Savage 2000 chip. Nvidia's own top-end graphics processor, the GeForce 256, also contains a transform and lighting engine, to improve game performance by taking complex geometry set-up operations off the host CPU. That said, of Nvidia's 27 patents, none specifically refer to T&L engines, so it could be anything. ® Related StoriesVia-S3 merger would make Intel really grumpyIntel grabs 3D Labs portfolio